The A, B, and O blood group antigens found on the surface of erythrocytes, are not confined to red cells but are found in most secretions and in many tissues of the human body. The immunodominant structure for the blood group A determinant, which is one of the most extensively studied specificities, is considered to be: ##STR1## However, it has been found that the remainder of the carbohydrate chain (R) has much influence on the precise specificity of the determinant. Different blood group A variant structures have been described which have different sugars and sugar sequences in the R region. See, e.g., Kabat, Carbohydrates In Solution, pp. 334-361 (H. S. Isbell, ed.) (American Chem. Society, Washington, D.C.) (1973); Watkins, Advances in Human Genetics, (H. Harris & K. Hirschorn, ed.), v. 10, pp. 1-136 (1980); Hakomori, Semin. Hematol., 18:39-62 (1981). For example, the A determinants (as well as the B, H. and Lewis determinants) are based on two different carbohydrate sequences, i.e., Gal.beta.(1.fwdarw.3)GlcNAc (1.fwdarw.3)Gal.beta.- or Gal.beta.(1.fwdarw.4)GlcNAc (1.fwdarw.3)Gal.beta.-. These structures, are designated type 1 and type 2 chains, respectively. More recently, a type 3 chain blood group determinant [extended or repetitive A: GalNac.alpha.(1.fwdarw.3)Gal.beta.(1.fwdarw.3)GalNAc.alpha.(1.fwdarw.3)Gal .beta.(1.fwdarw.4)GlcNAc] and a type 4 A chain based on the globo sequence [GalNAc.alpha.(1.fwdarw.3)Gal.beta.(1.fwdarw.3)GalNAc.beta.(1.fwdarw.3)Gal .alpha.(1.fwdarw.4)Gal] have been described by Causen et al., PNAS 82:1199-1203 (1985); Biochem Biophys Res. Commo. 124:523-529 (1984). FIG. 1 illustrates various forms of the A antigen.
These human blood group antigens have traditionally been detected with allogeneic sera, which contains polyclonal antibodies with heterogeneous specificities. The technique for formation of hybridomas which produce monoclonal antibodies specific for particular antigens has made it possible, however, to conceive of the possibility of detecting blood group antigens using monoclonal antibodies, rather than allogeneic sera.
Voak et. al., Vox Sang 46:185-198 (1980), and Messetu, et. al., Vox Sang 46:185-198 (1984), have reported producing monoclonal antibodies to specific blood group antigens. Additionally, Barnstable, et. al., Cell 14:9-20 (1978); Edelman, et. al., Immunol. 44:549-555 (1981); and Abe, et. al., J. Immunol. 132:1951-1954 (1984), have all described monoclonal antibodies to the type A blood group antigens. For only a few of these, however, have specific antigenic determinants been recognized.
Recognition of different epitopes of the varieties of particular blood group antigens is now becoming recognized as important, however, because cells, cancer cells in particular, can express a variety of type A antigenic determinants on their surfaces which cannot be determined by conventional reagents. Determination of different antigenic determinants makes it possible to analyze the expression of A antigens, variants in normal and tumor samples, and allow one to search for alterations of expression in malignancy.
Hence, it is an object of this invention to provide a method of distinguishing between different types of type A blood group antigens, using monoclonal antibodies.
It is a further object of this invention to provide a panel of monoclonal antibodies which can be used to distinguish different type A blood group antigens.
The first object of the invention can be accomplished on any type of cell or tissue but is particularly useful in analysis and diagnosis involving cancer cells and tissues.
The monoclonal antibody panel of the invention may be used, as will be seen infra, to distinguish type A blood group antigens in extreme detail.
How the objects of this invention are accomplished will be seen from the disclosure which now follows.